The finned Transpo 911 series of voltage regulator uses the same heatsink as old fashioned 70-amp rectifier "diode" isolators. It may be helpful to keep in mind that your regulator survives in ambient temperature conditions of 160+F Then add The temperature differential Delta T on top of that.
The TO5 style MOSFET is rated at 125 Celsius so no worries there. If the regulator voltage divider zener network is stable and the circuit does not incorporate thermistor compensation then voltage should be relatively stable from say 10c to 50c. Later models of the 540XHD use a 50-amp rated PNP MOSFET chip.
Adding a nice 470uf 50V cap at the reg A terminal and a 2.0uf 50V cap at the I terminal dampens a nervous regulator. Adding a reversed bias MR2535 avalanche rectifier from regulator F terminal to chassis negative helps eliminate field circuit tanking after abrupt alternator output load removal. Do not add a capacitor of any type to the F terminal circuit.
